Self-steering railway bogie

ABSTRACT

The invention relates to railway bogies, and more particularly, but not exclusively to a self-steering bogie for a locomotive. In accordance with the invention there is provided a self-steering railway bogie ( 1 ) comprising leading and trailing wheelset ( 2.4 ) having two ends ( 3,5 ) and a frame for limiting the movement of the wheelset ends. The bogie is provided with a number of fluid cylinders ( 7 ) attached between the wheelset ends and the frame, and fluid flow means ( 8 ) between the cylinders allowing wheelsets to yaw inversely relative to each other and restricting other relative movement of the wheelsets.

FIELD OF THE INVENTION

This invention relates to railway bogies, and more particularly, but not exclusively to a self-steering bogie for a locomotive.

BACKGROUND TO THE INVENTION

It is generally accepted that the direct cost of maintaining wheels on a bogie can be between 25% and 40% of total bogie maintenance cost. A great deal of time and effort is expended all over the world in developing bogies with lower track forces and smaller incidence angles between the wheels and track and thus less track and wheel wear. On locomotives, wagons and coaches wheel wear amounts to up to 40% of the life cycle cost per vehicle alone and is even more significant if the total operational cost of energy, infrastructure, equipment utilization and capital cost is considered.

Self steering bogies are known in the art. The technology in its simplest form has been used on freight and coach bogies for many years and is described in U.S. Pat. No. 4,067,261 in the name of Scheffel entitled “Damping Railway Vehicle Suspension”, the contents of which is incorporated herein in its entirety by way of reference. Self-steering usually involves so called “cross-anchor” members which connect diagonally opposing axleboxes on leading and trailing wheelsets with levers, rods or links. Several other patents, for example U.S. Pat. Nos. 4,067,261; 4,067,062; 4,735,149; 5,588,367 PCT/IB99/01890, PCT/IB99/01383 and WO 00/07864 to Scheffel, also U.S. Pat. No. 6,871,598 to Schaller et al. which describes the mechanics in bogies (trucks) and systems to achieve superior curving and stability performance.

Wheelsets with conical or profiled treads, which are allowed some yaw freedom, can align themselves radially on a curved track through a difference of rolling diameters on the inner and outer wheels of an axle to guide a railway vehicle around a curve. This is referred to in the art as “off flange” curving, as the wheelsets are substantially free to align themselves with the track and utilise the conicity of profiled treads and it is not necessary for a wheel flange to contact the track during curving. It is thus desirable for wheelsets to be constrained in the horizontal plane, longitudinally, whilst allowing a degree of relative wheelset yaw to enable self-steering. This is achieved by suspending the axleboxes, which house the journals of the wheelsets, with elastic constraint means or so called “shear blocks” to a bogie frame. Shear blocks allow a limited degree of movement of the wheelsets relative to the frame within the horizontal plane in all directions. It is further desired that a rail vehicle (wagon, coach or locomotive) negotiates tangent track at maximum allowable operating speed for the existing track conditions, in a stable running mode and negotiate curved track with the minimum of lateral creep forces. Because curved track amounts, on average, to 40% of a total journey length, good tracking on curved track is necessary. Good tracking leads to reduced wear and tear on all railway systems; overhead conductor, permanent way and rolling stock. Good tracking maximizes adhesion utilization both on curves and tangent track.

Off-flange curving bogies offer significant advantages over conventional bogies in that it facilitates wheelset yaw against a low stiffness value, constrains relative lateral movement of wheelsets or so called “inter axle shear stiffness” and also parallel wheel yaw or “parallelogramming”, which results in decreased “hunting” of the wheelsets, lower track and rail forces and thus a higher maximum speed, and increased service life of wheelsets.

Though the cross-anchor configuration is suitable for bogies used on freight or trailer coach cars, motorised coach and locomotive bogies often have wheelsets which are individually driven by electric traction motors or elaborate brake systems. These traction motors or brake systems take up additional space on the bogie between wheelsets which makes it laborious to install cross-anchor members. It is especially difficult to install the cross-anchor members in the same horizontal plane as the axle boxes which is the most effective position. A similar problem is encountered with bogies having 3 axles.

The problem above has been addressed in various forms. One approach is disclosed in U.S. Pat. No. 5,588,367 in the name of Scheffel, generally referred to in the industry as the Frame-Mounted-Shear-Stiffener (FMSS), which discloses levers and links connecting wheelsets outboard of the space between wheels. This allows the space between the wheelsets to be used for traction and/or brake gear. A disadvantage of this approach is that the implementation thereof is a complex arrangement of levers and links for connecting wheelsets.

OBJECT OF THE INVENTION

It is an object of this invention to provide a self-steering railway bogie that, at least partially, alleviates some of the problems associated with the prior art and/or offers an alternative to conventional self-steering railway bogies.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a self-steering railway bogie comprising:

-   -   a leading wheelset having two ends;     -   a trailing wheelset having two ends;     -   a frame for limiting the movement of the wheelset ends;     -   a number of fluid cylinders attached between the wheelset ends         and the frame; and     -   fluid flow means between the cylinders allowing wheelsets to yaw         inversely relative to each other and restricting other relative         movement of the wheelsets.

The hydraulic cylinders are double-acting cylinders having operatively front and rear chambers and a piston between the front and rear chambers.

The chambers have the same rate of change in volume with piston travel. Each chamber has hydraulic connection means for connecting a hydraulic line, such as a pipe or a tube, which forms part of the fluid flow means.

The fluid flow means allow the cylinders to move such that diagonally opposing cylinders correspond to each other.

In a first arrangement of the fluid flow means, the operatively front chambers of the hydraulic cylinders attached between the frame and the leading wheelset ends are hydraulically connected. Similarly the operatively front chambers of the hydraulic cylinders attached between the frame and the trailing wheelset ends are hydraulically connected. The operatively rear chambers of the cylinders on a side are hydraulically connected, and also the operatively rear chambers of the cylinders on an opposing side are connected.

In a second arrangement of the fluid flow means, the operatively front chambers of the cylinders attached between the leading wheelset ends and the frame are hydraulically connected and the operatively rear chambers of the hydraulic cylinders attached between the rear wheelset ends and the frame are hydraulically connected. The rear chamber of the cylinders attached to the leading wheelset on a side is hydraulically connected to the front chamber of the cylinder attached to the trailing wheelset on an opposing side.

In both arrangements above, the chambers are cross and diagonally connected.

A further feature of the invention is that the hydraulic cylinders and fluid flow means can be retrofitted to currently existing bogies.

The retrofitting may be done by replacing rigid axle box links with hydraulic cylinders of corresponding size.

The cylinders may be attached longitudinally.

The cylinders may be attached diagonally. Preferably the cylinders are mounted diagonally so that imaginary axes through opposing leading and trailing cylinders intersect at the centre of the bogie.

The diagonally attached cylinders also restrain relative lateral movement of the wheelsets without a disturbing moment on the frame.

Cylinders can also be mounted at an angle between purely longitudinal and fully diagonal positions.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is described below by way of example only and with reference to the drawings in which:

FIG. 1 is a schematic representation of a first arrangement of hydraulic cylinders and fluid flow means of a self steering railway bogie;

FIG. 2 is a schematic representation of a second arrangement of hydraulic cylinders and fluid flow means of a self steering railway bogie;

FIG. 3 is a schematic representation of the second arrangement of hydraulic cylinders and fluid flow means showing diagonally mounted cylinders;

FIG. 4 is a perspective view of a three axle bogie from above showing enlarged views of cylinders; and

FIG. 5 is a perspective view the three axle bogie from below showing the enlarged views of cylinders;

FIG. 6 is a top view of a three axle bogie;

FIG. 7 is a side view of a three axle bogie with angled cylinders;

FIG. 8 is a perspective view of a two axle bogie with longitudinal cylinders from above;

FIG. 9 is a perspective view of the two axle bogie from below showing enlarged views of leading and trailing cylinders;

FIG. 10 is a bottom view of the two axle bogie; and

FIG. 11 is a side view of the two axle bogie.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to the drawings, in which like features are indicated by like numerals, a self-steering railway bogie is generally indicated by reference numeral 1.

The self-steering railway bogie 1 has a leading wheelset with two wheelset ends 3, one being an operatively right end 3R and the other being an operatively left end 3L. The bogie 1 also has a trailing wheelset 4 with two wheelset ends 5, one being and operatively right end 5R and the other being an operatively left end 5L. A frame 6, which includes axle boxes mounted on elastic constraint means in the form of shear blocks, limits the movement of the wheelset ends (3 and 5), particularly, the frame and shear blocks allow limited movement of the wheelset ends (3 and 5) in a substantially horizontal plane, whilst restricting vertical movement thereof.

A number of fluid cylinders 7 are attached between the wheelset ends (3 and 5) and the frame 6. The cylinders which are attached to the leading wheelset are indicated by 7L, 7LL indicates the cylinder attached to the wheelset end on the operatively left side and 7LR indicates the cylinder attached to the operatively right side. Similarly, the cylinders attached to the trailing wheelset are indicated by 7T, 7TL and 7TR respectively. The cylinders 7 are double acting cylinders, each having an operatively front chamber and an operatively rear chamber. Hereinafter, for ease of reference, the operatively front chamber of the cylinders will be indicated by suffix “F” and the operatively rear chamber of the cylinder will be indicated by suffix “R”, for example, the operatively front chamber of the cylinder attached to the wheelset end on the operatively left side of the leading wheelset 2 is indicated by 7LLF and the operatively rear chamber of the same cylinder is indicated by 7LLR.

The cylinders are connected by fluid flow means in the form of hydraulic tubes 8. The fluid flow means is arranged between the cylinders, and particularly between the respective chambers of the cylinders, to allow wheelsets (2 and 4) to yaw only inversely relative to each other and restricting other relative movement of the wheelsets (2 and 4).

In a first arrangement of the fluid flow means 8 the operatively front chambers of cylinders attached to the leading wheelset are hydraulically connected by a hydraulic tube 8.1 between chamber 7LLF and chamber 7LRF. As the hydraulic tubes 8 provides the hydraulic connection between the two chambers (7LLF and 7LRF), a fixed combined amount of hydraulic fluid will always be present in the two chambers (7LLF and 7LRF). In other words, if the volume of chamber 7LRF decreases, the volume of chamber 7LLF will increase by the same amount. Similarly the operatively front chambers of the cylinders attached to the trailing wheelset are hydraulically connected by a hydraulic tube 8.2 between chambers 7TLF and 7TRF. The operatively rear chambers of the cylinders on the left side of each wheelset end are hydraulically connected by hydraulic tube 8.3 between chamber 7LLR and 7TLR and the operatively rear chambers of the cylinders on the right side each wheelset end are hydraulically connected by hydraulic tube 8.4 between chambers 7LRR and 7TRR.

In use, the first arrangement of the fluid flow means described above allows the wheelsets to yaw only inversely relative to each other. For example (referring to FIG. 1), when the bogie is on a track which curves left, the leading wheelset 2 will be inclined to yaw counter clockwise as a result of the forces between the wheels and the track. When the leading wheelset yaws counter-clockwise, the volume of chamber 7LLF will tend to increase and the volume of chamber 7LRF will tend to decrease. The volume changes are enabled by the hydraulic tube 8.1 and fluid is transferred from chamber 7LRF to chamber 7LLF. The resulting change in volume of 7LLR is enabled by hydraulic tube 8.3 which transfers fluid from chamber 7LLR to 7TLR. Similarly, the resulting change in volume of chamber 7TLF is enabled by hydraulic tube 8.2 which transfers fluid from chamber 7TLF to chamber 7TRF. Finally, the resulting change in volume of chamber 7TRR is enabled by hydraulic tube 8.4 which transfers fluid from chamber 7TRR to chamber 7LRR. The chambers and fluid flow means forms a closed system wherein all chambers have the same initial volume and volume changes are transferred through the hydraulic tubes 8 to all chambers to reflect wheelset yaw inversely relative to each other. Thus, in the current example, the volumes of chambers 7LRF, 7LLR, 7TLF and 7TRR are equal and smaller than the volumes of chambers 7LRR, 7LLF, 7TLR and 7TRF which are necessarily also equal and the amount of counter-clockwise yaw of the leading wheelset is equal to the amount of clockwise yaw of the trailing wheelset.

It will be appreciated that in the example above, the fluid flow means need not be exactly arranged as described in the example and any arrangement of the fluid flow means whereby diagonally opposing cylinders correspond to each other and the fluid flow means forms a closed system will achieve the desired results. For example (as shown in FIG. 2), where chambers 7LRF and 7LLF are hydraulically connected, chambers 7TRR and 7TLR are hydraulically connected, and chamber 7LRR is hydraulically connected to chamber 7TLF, and chamber 7LLR is hydraulically connected to chamber 7TRF. Wheelset yaw will be inversely reflected by the leading and trailing wheelsets.

The descriptions above relate to the inverse yaw of leading and trailing wheelsets which is a crucial element of self-steering. In addition to allowing inverse yaw, the fluid flow means must also restrict other relative movements of the wheelsets, particularly to keep wheelsets longitudinally stable during traction, or braking, and also to prevent parallel yaw of the wheelsets (so-called “parallelogramming”). Both arrangements of the fluid flow means restrict such undesirable movements, as the fluid flow means forms a closed system which locks any movement which is not inverse yaw, similar to conventional cross-anchor arrangements. In the arrangement shown in FIG. 3, wherein the fluid cylinders are mounted diagonally, such that imaginary axes through diagonally opposing cylinders intersect at the centre of the bogie, the wheelsets are also restrained from lateral movement relative to each other, which increases “inter axle shear stiffness” as it is referred to in the art. Any arrangement wherein the cylinders are mounted at an angle to the longitudinal center line of the bogie will provide a degree of resistance to lateral movement of the connected wheel sets in opposite directions or inter-axle shear stiffness. If the cylinders are mounted longitudinally wherein the angle between the cylinders and the longitudinal center line of the bogie approaches zero, other sub-systems, such as the horizontal-lateral suspension stiffness, lateral axle box stops or longitudinal inter-wheel set structures such as bissels, could provide adequate inter-axle shear stiffness for some operating situations such as slow speed operation.

External yaw dampers may be attached to the wheelset ends to provide damping of the cylinders. The hydraulic tubes 8 may also be dimensioned to restrict flow in the pipes to provide damping. The requirement for damping is related to the inter-axle shear stiffness and higher inter-axle shear stiffness may alleviate the need for damping.

The arrangement shown in FIG. 3 is operationally efficient, but it is usually problematic to position the cylinders so that the imaginary diagonals intersect at the center of the bogie. The arrangement of FIGS. 1 and 2, showing cylinders mounted longitudinally, do not provide the bogie with inter axle shear stiffness through the hydraulic connections. The inter axle shear stiffness would need to be provided by other means discussed above if required. With the longitudinal cylinders the inter-axle shear stiffness between axles due to the hydraulic system will be the same as for the bogie with solid axlebox links.

The arrangement of cylinders and fluid flow means described above allows for some of the mechanical elements of a conventional bogie, such as cranks and levers of the wheel set guidance system, to be disposed of. A further advantage of the arrangement over conventional mechanical components is a ‘stiffer’ connection between the wheel sets and a reduction of lost motion resulting from free-play, wear and elasticity inherent in mechanical systems. The arrangement requires less space and provides for connections over larger distances between connected wheel sets, for example a 3-axle bogie in which in which a mechanical anchor extending across the center axle is difficult.

A further feature of the invention allows cylinders and fluid flow means to be retrofitted to existing bogies. Providing a conventional on-flange curving design bogie with the cylinders and fluid flow means discussed above, will convert the bogie to an off-flange curving design in a cost effective manner. This may be done by replacing currently existing rigid axle box links with hydraulic cylinders of corresponding size. This is shown in FIGS. 4 to 11.

FIGS. 4 to 7 show a currently existing three axle bogie, specifically of the type having three powered axles, each individually driven by traction motors, designated by International Union of Railways (UIC) classification Co′. In these types of bogies it is especially difficult to allow the leading wheelset 2 and the trailing wheelset 4 to yaw inversely relative to each other with conventional cross-anchor members and will require a substantial re-design of the frame 6. Using fluid cylinders 7 which correspond in size to existing axle box links on these bogies and fluid flow means as described in the arrangements above, specifically the fluid flow means shown in FIG. 3, wherein the cylinders are diagonally mounted, the axle-boxes are provided with yaw freedom and necessary restraint to allow self-steering.

FIGS. 8 to 11 show a two axle bogie designated by UIC classification Bo′. The drawings show the axle box links replaced with cylinders of corresponding size and longitudinally mounted cylinders. The cylinders are hydraulically connected according to the arrangements described above to allow inverse yaw of the leading and trailing wheelsets. The cylinders are mounted in a longitudinal direction similar to the arrangements shown in FIGS. 1 and 2 and inter axle shear stiffness is provided by the existing axle box lateral stop arrangement.

In a further arrangement, it is possible to separate steering and normal traction and braking forces. The yaw motion of the wheel set can be accommodated by a balancing beam or bell crank/cross rod arrangement that will transmit the longitudinal traction and braking forces from wheelset to frame. The steering forces (forces to ensure opposite sense yaw, prevent same sense yaw, provide inter-axle shear stiffness) can be accommodated with a separate hydraulic system as in FIG. 3.

It is envisaged that the invention will provide a self steering bogie which alleviates design difficulties currently prevalent in motorised and 3-axle bogie design. It is further envisaged that the invention will provide an economical alternative to current complex self steering bogies and providing increased efficiency compared to mechanical systems. The retrofitting aspect of the invention will also allow implementing these systems in already existing bogies.

The invention is not limited to the precise details as described herein. For example, instead of using hydraulic tubes, hydraulic pipes, or any other hydraulic connection means maybe used. Further, the wheelset ends need not be attached to the frame with shear blocks any suitable elastic constraint means may be used. 

1. A self-steering railway bogie comprising: a leading wheelset having two ends; a trailing wheelset having two ends; a frame for limiting the movement of the wheelset ends; a number of fluid cylinders attached between the wheelset ends and the frame; and fluid flow means between the cylinders allowing wheelsets to yaw inversely relative to each other and restricting other relative movement of the wheelsets, wherein the hydraulic cylinders are double-acting cylinders having operatively front and rear chambers, the operatively front chambers of the hydraulic cylinders attached between the frame and the leading wheelset ends are hydraulically connected, the operatively front chambers of the hydraulic cylinders attached between the frame and the trailing wheelset ends are hydraulically connected, the operatively rear chambers of the cylinders on a side are hydraulically connected, and the operatively rear chambers of the cylinders on an opposing side are connected.
 2. The self-steering railway bogie of claim 1 wherein the hydraulic cylinders have a piston between the front and rear chambers.
 3. The self-steering railway bogie of claim 2 wherein each chamber has hydraulic connection for connecting a hydraulic line which forms part of the fluid flow means.
 4. The self-steering railway bogie of claim 3 wherein the fluid flow means allows the cylinders to move such that diagonally opposing cylinders correspond to each other.
 5. The self-steering railway bogie of claim 3 wherein the cylinders are attached in a horizontal plane at axle center height.
 6. The self-steering railway bogie of claim 3 wherein the hydraulic cylinders and fluid flow means are retrofitted to an existing bogie.
 7. A method of retro fitting a bogie, having a leading and trailing wheelset, with a hydraulic steering system comprising the steps of: replacing rigid axle box links with hydraulic cylinders of corresponding size; and providing the hydraulic cylinders with fluid flow means between the cylinders for allowing wheelsets to yaw inversely relative to each other and restricting other relative movement of the wheelsets, wherein the cylinders are attached longitudinally.
 8. A method of retro fitting a bogie, having a leading and trailing wheelset, with a hydraulic steering system comprising the steps of: replacing rigid axle box links with hydraulic cylinders of corresponding size; and providing the hydraulic cylinders with fluid flow means between the cylinders for allowing wheelsets to yaw inversely relative to each other and restricting other relative movement of the wheelsets, wherein the cylinders are attached diagonally.
 9. The method of claim 8 wherein the cylinders are mounted diagonally so that imaginary axes through opposing leading and trailing cylinders intersect at the center of a bogie. 10-11. (canceled)
 12. The self-steering railway bogie of claim 2 wherein the fluid flow means allows the cylinders to move such that diagonally opposing cylinders correspond to each other.
 13. The self-steering railway bogie of claim 12 wherein the cylinders are attached in a horizontal plane at axle center height.
 14. The self-steering railway bogie of claim 13 wherein the hydraulic cylinders and fluid flow means are retrofitted to an existing an existing bogie.
 15. The self-steering railway bogie of claim 12 wherein the hydraulic cylinders and fluid flow means are retrofitted to an existing an existing bogie.
 16. The self-steering railway bogie of claim 1 wherein the fluid flow means allows the cylinders to move such that diagonally opposing cylinders correspond to each other.
 17. The self-steering railway bogie of claim 16 wherein the cylinders are attached in a horizontal plane at axle center height.
 18. The self-steering railway bogie of claim 17 wherein the hydraulic cylinders and fluid flow means are retrofitted to an existing an existing bogie.
 19. The self-steering railway bogie of claim 16 wherein the hydraulic cylinders and fluid flow means are retrofitted to an existing an existing bogie.
 20. The self-steering railway bogie of claim 1 wherein the cylinders are attached in a horizontal plane at axle center height.
 21. The self-steering railway bogie of claim 1 wherein the hydraulic cylinders and fluid flow means are retrofitted to an existing an existing bogie. 